1. Field of the Invention
The present invention relates to a key telephone system, and more specifically to a key telephone system by which telephone-related data (e.g., speed dial telephone numbers) stored therein and used before a terminal telephone set is moved can be used as they are even after having been moved.
2. Description of the Prior Art
In the key telephone sets, when the terminal telephone sets (referred to as terminal set, hereinafter) are moved in an office, for instance, it is necessary to change ports of a key service unit so that the terminal sets can be reconnected to corresponding ports thereof. In this case, when the ports are changed, since the customer data areas (referred to as data area, hereinafter) of a memory incorporated in the key service unit are different according to the terminal sets, the customer data (referred to as data, hereinafter) used before the terminal sets are moved cannot be used as they are after movement. Therefore, after the terminal sets have been moved, it has been so far necessary to rewrite data to be stored in the memory of the key service unit, thus causing a troublesome work for the users.
To overcome this problem, conventionally, the following apparatus as shown in FIGS. 1 to 3 has been proposed. In FIG. 1, a terminal set 10 is provided internally with dip switches 11 as shown in FIG. 2 to indicate an ID code allocated to the terminal set. Further, the key service unit is provided with an internal memory 12 as shown in FIG. 3. In FIG. 3, the memory 12 has data areas 13a to 13n corresponding to a plurality of terminal sets and ports. 13aa to 13nn corresponding to the respective data areas. Therefore, when a terminal set is connected to a port, the key service unit discriminates the ID code of the connected terminal set, and further enables the data stored in the data area corresponding thereto to be used. Further, when a terminal set connected to the port 13aa is moved and thereby reconnected to the port 13bb (vacant port), for instance, the key service unit discriminates the ID code of the moved terminal set, and further overwrite the data stored in the data area 13a in the data area 13b.
In the conventional method as described above, since the dip switches must be provided for the respective terminal sets, there exists a problem in that the cost thereof inevitably increases. In addition, since it has been necessary to set the ID codes of all the terminal sets with the use of the dip switches whenever the terminal sets have been installed, the setting work has been so far troublesome.
To eliminate the use of the dip switches, the following method has been known: the sequence that the terminal sets are disconnected from the key service unit is stored in the memory 12; and when the terminal sets are connected to the ports in accordance with the stored disconnection sequence, the key service unit recognizes the terminal sets and further overwrite the data in the new data areas. In this method, however, since it is necessary to correctly store the sequence that the terminal sets are extracted by the user, the installation work is also troublesome increasingly with increasing number of the terminal sets.